The present invention relates in general to semiconductor optocoupler device packages and, more particularly, to the architecture of a surface mount package single plane leadframe.
Semiconductor optocouplers are used extensively to couple electronic signals between low voltage circuits and high voltage circuits. The optocoupler offers an advantage of providing electrical isolation between the two circuits, thus reducing interface problems that are commonly known in the art. An example of such an application is the interface between an electric motor and a microprocessor used to control the motor. It is not only advantageous to control the motor with the microprocessor, but it is also beneficial to provide feedback to the microprocessor as to the operating status of the motor. This type of application requires at least a pair of optocouplers to successfully perform the interface function.
In the past, optocouplers have been packaged in TO-5, TO-18, and in 8-lead dual in-line packages. Due to industry views of JEDEC standard case outline size and footprint limitations, coupled with UL1577 and VDE884 standards constraints, only one optocoupler pair could be housed effectively in a given package. Thus two packages are required to facilitate a desired motor application. Furthermore, the TO-5, TO-18, and dual in-line packages are inherently expensive. Extra expense is incurred in the optocoupler dual in-line configuration because two lead frames are required to facilitate mounting of more than one optocoupler pair in the smaller JEDEC outline limited space. With this technology, each component of the optocoupler pair is mounted on its respective lead frame in opposition to the other component. This configuration leads to other manufacturing problems such as optocoupler component alignment. Because of footprint constraint, this package implementation cannot facilitate the requirement of two optocoupler pairs in one package. Therefore, a cost effective solution has not been achieved for practical applications of optical isolation.
To further reduce the cost of an optocoupler system, it is also desirable to miniaturize the system by migrating toward surface mount component technology. It is generally known in the art that surface mount technology is more cost effective from both a manufacturing and component viewpoint.
Hence, a need exists for a small outline surface mount package having a single plane leadframe architecture that is capable of accommodating multiple optocoupler device die pairs.